Mention `sleep` in `thread.pause` description. Fixes: #4276 · savonet/liquidsoap@6a86d5b

Canceling since a higher priority waiting request for 'CI-refs/heads/main' exists

The operation was canceled.

Unexpected input(s) 'opam-depext', valid inputs are ['allow-prerelease-opam', 'ocaml-compiler', 'opam-repositories', 'opam-pin', 'opam-local-packages', 'opam-disable-sandboxing', 'dune-cache', 'cache-prefix', 'github-token']